Internal combustion engines, including diesel engines, gasoline engines, gaseous fuel-powered engines, and other engines known in the art are generally designed to operate within a particular speed range. When an engine operates uncontrollably at a speed greater than the design range, the engine is considered to be “running away”. As an engine runs away, forces acting on components of the engine can increase to damaging levels. One situation in which an engine can run away includes operation of the engine within potentially explosive atmospheres, such as those found in petroleum, coal, or natural gas mining and reclamation applications. In these atmospheres, it may be possible for the engine to draw in and combust hydrocarbons from the atmosphere in an unregulated manner, thereby causing the engine to overfuel and speed past its intended design range.
Historically, a run-away engine was shut down manually to reduce damage to the engine caused by excessive speeds. In particular, when an engine was determined to be running away, an operator of the engine could manually move a valve or gate to block air (or air and fuel) flow into the engine, thereby shutting the engine down. Although this manual process was effective, it was error prone and often involved operator delay in detecting the run-away condition and activating the shutoff valve.
One attempt to improve shutdown of a run-away engine operating in a potentially explosive atmosphere is described in U.S. Pat. No. 7,444,982 issued to Rivet on Nov. 4, 2008 (the '982 patent). In particular, the '982 patent discloses a hydro-mechanical air shutoff for an internal combustion engine. The hydro-mechanical air shutoff includes a shutoff device connected to an air valve disposed within an intake of an engine, and a flyweight valve spool fluidly connected to the shutoff device. During an overspeed condition, the flyweight valve spool is caused to move by centrifugal force and block a passageway leading from the shutoff device, thereby causing system pressure to increase to a point where the shutoff device pushes the air valve closed and shuts down the engine.